Bathroom Duct Venting

By Robert Robillard on Bathrooms

Bathroom shower Vent

This article will address bathroom duct venting options.  The two most common ways to route duct work to vent bathroom moist air outside are:

1. through the ceiling and out through an exterior wall.
2. through the ceiling and out through the roof.

Of the two bathroom duct venting options. a vent through a wall, done properly, is less likely to leak.

Bathroom Duct Venting Bathroom Duct Venting
Image: hometips.com

In my travels I have seen many improperly vented bathroom fans and dryer ducts and hoods.Improper venting of a fan can cause moisture problems which can result in condensation forming within the vent, duct or house.

Condensation can run back down an improperly pitched duct, leaking around the fan, creating stains, causing structural rot problems or drip back out of the fan and into the room.

Bathroom Duct Venting
Photo: Improperly vented fan into attic. Notice mold on roof sheathing.

Do NOT Vent Into The Attic

Many builders and contractors take shortcuts and vent fans directly into the attic. This only fills the attic with mold causing moist air. The result is an increase in the possibility of attic mold and wood rot. In winter, frost forms in the attic surfaces and as the frost melts, water can damage the ceilings below.

If the attic framing allows, I feel that it is always better to install duct-work and vent the fan through the nearest soffit or gable side wall. This allows you to make the vent installation under the overhang of the roof, preventing the need for a roof vent.

A fan can be ducted to the soffit hood vent using flexible metal or solid duct material. I prefer to use the flexible metal or solid aluminum piping. [seams taped and installed facing up]

Installing a vent duct horizontally across the attic, and slightly pitched toward the outside hood reduces the possibility of condensation trickling back down around the fan.

Insulating the duct with insulation wrap also can reduce some of the formation of condensation within the duct.  Click here for more detail on bathroom duct venting options and vent duct work.

~ concord carpenter

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About the author

Robert Robillard

Carpenter / Remodeler / Editor

Rob Robillard is “The Concord Carpenter” Rob is a builder, general contractor, carpenter, woodworker, and editor of Concord Carpenter and ToolBoxBuzz As a General Contractor and carpenter, Rob owns and operates Concord Carpenter LLC. A full-service remodeling and construction company. Rob is a recognized leader in home building best practices and a source for how-to information for building professionals. On this website, Rob covers all aspects of home construction, building science, home improvement, woodworking, remodeling, and some of the best product and tool reviews. Rob is in charge of our Tool and Product Review series - Concord Carpenter Videos where we post all of our tool reviews and video tutorials. Rob approaches remodeling and building construction with a pragmatic and problem-solving approach. He enjoys using his knowledge and experience to help and educate building professionals as well as DIYers on best practices in the construction and remodeling industry. He's a strong advocate for "raising the bar" in the construction trades and promoting the trades to youth. #BeAMentor #Green2Great Craftsmanship, quality, and pride guide his journey on this channel The Concord Carpenter's motto: "Well done is better than well said!" : Read more about Rob If you have a building or remodeling question you can have rob respond to your answer via video. Click here for more information. https://jointruly.com/robillard Invite code: x22r2

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